U.S. Pat. No. 4,844,976 (Huang) relates to retroreflective sheeting that has been improved by a coating comprising silica and a transparent polymer selected from aliphatic polyurethanes, polyvinyl chloride copolymers having a minor amount of a comonomer containing at least one carboxylic acid or hydroxyl moiety, and acrylic polymers. Exemplified acrylic polymers include compositions based on acrylic polymers commercially available under the trade designations (“Neocryl A-614”), (“Neocryl A-612”), (“Neocryl A-601”) and (“Rhoplex E-1895 ”).
WO 00/68714 teaches a coating for a retroreflective document that renders the surface of the document receptive to toners and inks printed thereon while not substantially interfering with the retroreflective properties of the underlying substrate. In one embodiment, the coating comprises an aqueous based dispersion or emulsion of a crosslinkable acrylic acid polymer.
EP 0 615 788 A1 (Watkins) relates to a method for forming clear coats on retroreflective articles utilizing an aqueous coating composition comprising water, water-borne dispersion of polyurethane, and cross-linker, and optionally acrylic emulsion; retroreflective articles formed according to the method; and a liquid coating composition for use in the method and in making the articles.
U.S. Pat. No. 5,508,105 (Orensteen) relates to polymeric sheeting materials directly thermally printed upon with a thermal printing system and a polymer-based colorant/binder. The polymeric sheeting materials comprise a core sheet and a thermally print receptive surface on the core sheet. The thermally print receptive surface may be formed from compositions comprising a polyurethane dispersion optionally combined with an acrylic emulsion. The thermally print receptive surface is smooth, transparent, durable, and weatherable.